1. Field of the Invention
The present invention generally relates to single-use syringes in which medicament is filled preliminarily, i.e., so-called prefilled syringes and more particularly, to a prefilled syringe which is provided with a temporary stop means for temporarily stopping a plunger rod at a predetermined position when, in use, the plunger rod is depressed forwardly.
2. Description of the Prior Art
Prior to administration of injection liquid of a two-component type prefilled syringe in which powdery medicament and pharmaceutical liquid are, respectively, contained in front and rear compartments of a tubular body, a plunger rod is stopped temporarily in a state where the pharmaceutical liquid in the rear compartment has fully flowed into the front compartment by depressing the plunger rod. When the powdery medicament is sufficiently dissolved or dispersed in the pharmaceutical liquid by shaking the tubular body in this state, the injection liquid is prepared. Subsequently, by further depressing the plunger rod, the injection liquid is administered.
A prefilled syringe shown in FIGS. 17 and 18 is known from Japanese Utility Model Laid-Open Publication No. 7-7650 (1995). In this known prefilled syringe, a pair of bosses 61 are provided on an inner periphery of a flange 55a of a finger grip 55 mounted on an outer periphery of a rear end portion of a tubular body 52, while a pair of first stopper plates 65 and a pair of second stopper plates 66 are provided between neighboring two of crossed ribs 62 of a plunger rod 60 so as to not only abut on each other through a corresponding one of the ribs 62 but be axially spaced away from each other such that the plunger rod 60 is temporarily stopped by bringing the bosses 61 and the second stopper plates 66 into contact with each other.
However, in this known prefilled syringe, after the first stopper plates 65 have come into contact with the bosses 61 by inserting the bosses 61 through recesses 64 formed on a front end flange 63 of the plunger rod 60, the plunger rod 60 is pulled slightly rearwards and rotated so as to displace the bosses 61 to between the ribs 62 free from the first stopper plates 65. Then, by further depressing the plunger rod 60, the bosses 61 come into contact with the second stopper plates 66. Subsequently, after the bosses 61 and the second stopper plates 66 have been brought out of contact with each other by rotating the plunger rod 60 until the bosses 61 are positioned between the ribs 62 free from the second stopper plates 66, injection liquid is administered by further depressing the plunger rod 60. Therefore, this known prefilled syringe has such drawbacks that its construction is complicated and its operation is troublesome and difficult.
Meanwhile, Japanese Patent Laid-Open Publication No. 8-229122 (1996) discloses a prefilled syringe in which a forwardly obliquely and radially outwardly extending rodlike projection 70 is formed integrally with a plunger rod 75 as shown in FIG. 19. Even if an external force such as an impact force is applied to this prior art prefilled syringe during its storage, a front end of the rodlike projection 70 is brought into contact with a finger grip 73 so as to temporarily stop the plunger rod 75 such that inadvertent displacement of the plunger rod 75 is prevented. Consequently, such a phenomenon is eliminated that medicament filled in the prior art prefilled syringe undesirably linking from an injection needle is eliminated.
In the prior art prefilled syringe of FIG. 19, after the plunger rod 75 has been temporarily stopped, the rodlike projection 70 is inserted into a slot 76 of the plunger rod 75 such that a sharp edge 70a of a front end face of the rodlike projection 70 is brought into engagement with a recess 76a of the slot 76. Then, by depressing the plunger rod 75, injection liquid is administered. However, while the plunger rod 75 is being stopped temporarily, the front end of the rodlike projection 70 is held in contact with the finger grip 73. Thus, when an attempt is made to push the rodlike projection 70 downwardly in this state, the front end of the rodlike projection 70 is pressed against the finger grip 73 further powerfully, so that it is difficult to insert the rodlike projection 70 into the slot 76. As a result, in this prior art prefilled syringe, when the rodlike projection 70 is inserted into the slot 76, the rodlike projection 70 held in contact with the finger grip 73 should be spaced away from the finger grip 73 by retracting the plunger rod 75 and then, the rodlike projection 70 is required to be inserted into the slot 76. Therefore, this prior art prefilled syringe has such a disadvantage in that air is sucked into tubular body 71 from an injection needle upon retraction of the plunger rod 75.
Furthermore, in this prior art prefilled syringe, since the front end of the forwardly obliquely and radially outwardly extending rodlike projection 70 is brought into contact with a rear end face of the finger grip 73, the front end of the rodlike projection 70 is apt to slide upwardly on the rear end face of the finger grip 73, thereby resulting in an inconvenience in that the temporary stop of the plunger rod 75 becomes unstable.
Accordingly, an essential object of the present invention is to provide, with a view toward eliminating the above described drawbacks of conventional prefilled syringes, a prefilled syringe which is simple in structure and easy in operation, which eliminates a risk that air is sucked into a tubular body from an injection needle and which is provided with a temporary stop means capable of temporarily positively stopping a plunger rod.
In order to accomplish this object of the present invention, a prefilled syringe according to the present invention comprises: a tubular body which has an open front end and an open rear end; a front assembly which is mounted on an outer periphery of a front end portion of the tubular body; a finger grip which is mounted on an outer periphery of a rear end portion of the tubular body; a front sealing member which is provided in the tubular body so as to be disposed forwardly of injection liquid; a rear sealing member which is provided in the tubular body so as to be disposed rearwards of the injection liquid; a plunger rod which is provided so as to be movable in the tubular body; a temporary stop means for temporarily stopping the plunger rod through retention of the temporary stop means by the finger grip such that the rear sealing member is temporarily stopped at a predetermined position of the tubular body; and a retention canceling means for canceling the retention of the temporary stop means by the finger grip without moving the plunger rod.
The temporary stop means may be constituted by a retainer member which is elastically formed integrally with the plunger rod so as to project rearwards obliquely relative to an axis of the plunger rod and radially outwardly from the plunger rod and is retained by the finger grip upon contact of a base portion of the retainer member with a rear end face of the finger grip, while the retention canceling means may include a hollow which is formed on the plunger rod so as to receive the retainer member.